Both aqueous based and dry hard surface cleaners are known and useful for all purpose household cleaning, and often incorporate or provide a source of hypochlorite as an oxidizing agent because of its powerful bleaching and germicidal properties.
Clay-thickened, aqueous hard surface scouring compositions with hypochlorite are disclosed in U.S. Pat. No. 3,985,668, issued Oct. 12, 1976, to Hartman and in U.S. Pat. No. 4,051,055, issued Sept. 27, 1977, to Trinh et al. Such hypochlorite containing aqueous hard surface cleaners may include an abrasive, as disclosed by U.S. Pat. No. 4,051,056, issued Sept. 27, 1977, to Hartman, where inorganic colloid-forming clays are utilized as suspending agents for the expanded perlite abrasive material.
An aqueous solution of sodium hypochlorite is inherently basic as it is the salt of a weak acid (hypochlorous acid) and a strong base (sodium hydroxide). As is well known, hypochlorite ion is stabilized by basic solutions, and thus hard surface cleaners containing hypochlorite as oxidizing agent typically have a pH of greater than about 8.
Peroxymonosulfate is known to be an oxidizing agent, but its use in scouring cleansers has typically been in dry form with a halide salt. For example, U.S. Pat. No. 3,458,446, issued July 29, 1969, to Diaz discloses a dry scouring cleanser whose solid constituents include potassium monopersulfate and a bromide salt. As is well known, potassium monopersulfate and either a chloride or a bromide salt react in the presence of water to form hypochorite or hypobromite respectively. Dry compositions where bromide is oxidized by peroxymonosulfate to form hypobromite following dissolution in aqueous solution are also disclosed in U.S. Pat. No. 4,028,263, inventor Gray, issued June 7, 1977.
These prior known, dry compositions including peroxymonosulfate and a water-soluble halide salt to provide a source of hypohalite have typically had an alkaline pH when dissolved in water. Dry scouring compositions are awkward to use on vertical surfaces and on curved surfaces, such as plumbing, for removal of rust and mineral stains.